Hey guys,
I have a 2003 F150 4x4 5.4 ex cab. The last few months, the back of my truck has been bouncing bad. Speed doesn't matter, every bump will make the back end bounce like crazy, heck even dropping or closing the tail gate will make it bounce. I've replaced the shocks at all 4 corners, rear shocks have been replaced with 3 different sets trying to rule out bad shocks out of the box, new leaf springs and shackles and hangers look good. I've checked the cab mounts, checked for cracks in the frame or anything loose. It has me stumped, any help, input, suggestions of stuff to look at is welcome!!!
Thanks!!

 

my daughters 2006 SC did that. I found a broken belt in one rear tire. Tires were about shot, i replace, problem GONE.

 

I wish that's what it was. I have a new set of Goodyear Duratrac's on it. After I replaced the shocks the first time, I thought it was the tires so they were replaced under warranty and it still bounces. Just to make sure it wasn't the "aggressive" tires like the dealership told me, I put the whole truck in the air on jack stands under the axle and a-arms and it still does it. It really has me stumped. I think I've put more miles on my creeper rolling around under the truck then I've put on the truck itself in the last month LOL

 

I would be checking the springs and hangers "real" close.

 

If you can stand in the rear of the bed area, and bounce it easily by bending your knees and bouncing, get a friend up there to boogie while you crawl under the rear and look around.

If you've got that much bounce, it shouldn't be hard to find, maybe missing the obvious. Yes, check springs and hangers like critter suggests.

Check the upper mounting points on the truck for the shocks, not rusted through or flexing, are they?
All these shocks that have been put on, were they bolted tight enough to properly swell the rubber bushings?

 

Springs are brand new, hangers and shackles all look good but I plan on replacing the shackles anyways. The shocks are tightened down properly. It is kind of hard to describe, it's not bouncing like there's no shocks in it at all. Just sitting in the garage, it maybe bounces up and down 3/4-1". The one thing I did notice, if i close the tailgate a little harder then normal, it almost looks like there is a hinge between the cab and box like the frame is flexing but I know it is not and made me start thinking possible rear cab mounts.

 

check the box mounts too along with the cab mounts.
like others are saying...get a buddy to bounce / dance in the bed while you check things out below.

maybe go as far as the tranny mounts

 

Well I still haven't figured out whats wrong. I've been under the truck while someone is bouncing it and I cant find anything obvious. Could a wore out cab mount cause something like this?

 

The chassis is suspened on the springs.
Shocks only dampen the movement between them.
I fail to see how a new set of shocks would not change the situation as I understand it, while the truck is at rest.
Shocks come in either single action standard or gas filled and in some cases a dampening in both directions as a reduced percentage for performance shocks.
Are the shock mounts broken or the frame broken out at the top?
You can't fail to see where the issue is if you look long enough.
Obviously not tires when the truck is setting still.
I'm not trying to insult your intellgence but your missing it some place.
Good luck.

 

No insult taken at all. I am hoping its something obvious that I'm just missing but who knows. It is really hard to describe the problem, almost one of those things you have to see . Its more of a "wiggle" up and down then a bounce, is about the best way I can describe it. The more I play with it tho, the more I get stumped. Shocks new, leaf springs new, shackles and hangers good, no cracks in the frame or shock mount. About the only thing I can see that doesnt look quite right to me is the back of the cab seems to bounce or "wiggle" more then it should. Now I just need to get another T-50 Torx so I can take the back seat out to get to the bolts for the cab mounts

 

with your buddy bouncing in the bed.. crawl under the truck and with one hand span between the frame and cab body by the rubber mounts. if you feel quite a bit of flex between your thumb and fingers, you will know its the mounts.

 

LINK REMOVED
Reported.

If it is the mounts then at least you will have a good reason to go out get a set of polyurethane body mounts.

 

What type of shock are you putting on it? The body mount is probably broke at the cab. Had the little woman move around in the box while slowly driving back road she noticed the movement of a bad mount area so replacing the mount fixed the bloop-bloop-bloop/flip-flop. Maybe overload at the tail gate caused it?

 

Mudslinger, did you ever find the problem? I have the same thing and I'm going to end up in the looney bin right along with you. I did shocks, tires and I'm in the process of doing U-Joints. I'll check back in when I get it done.

 

U-Joints helped with some things, but not the bouncing. Shifting from Reverse to Drive is MUCH smoother, but that stinkin' bounce is still there. So it was a necessary repair, but didn't take care of the problem I was working on.